Inclusion and Exclusion
Besides meeting minimum thresholds for caregiving (mentioned in the "How is caregiving defined" section), participants in intervention studies may need to have some minimal level of distress or impairment.
Interventions often target particular problems (e.g., depression, anger) for which participants must meet criteria through screening. This step is undertaken to ensure that the sample has the problem targeted by the intervention.
Without such eligibility criteria, there is a risk that participants will not have sufficient distress to show improvements on dependent variables, such as depressive symptoms, due to floor effects.